| 论文摘要 |
In this study, a new genus and species of euharamiyidans, Qishou jizantang gen. nov. et sp. nov., is reported from the Jurassic Yanliao Biota, China. The new taxon has a non-basined, ultimate upper premolar with an extra labial cusp denoted as AA1(C1). It is similar to Shenshou in that it has proportionally small cheek teeth and an occlusal pattern similar to the M2/m2 pattern in multituberculates. Qishou gen. nov. differs from Shenshou in having a tricuspid upper incisor, molars with many more cusps and that the a1 cusp of the lower molars mesially aligns with the row-b cusp. The mandible of Qishou does not have a postdentary trough, consistent with an ectotympanic without an anterior limb. Another old, skeletal specimen has been determined to represent another unidentified Qishou species. A new family, Shenshouidae, is proposed, based on the type genus Shenshou, and includes Qishou. A comparison is made between shenshouids and other genera or specimens assigned to ‘haramiyidans’. Shenshouids are more derived than Late Triassic ‘haramiyidans’ as they have fewer teeth with more complex tooth structures, but are relatively primitive among known Jurassic euharamiyidans, as they have the M2/m2 occlusal pattern of multituberculates and less-specialized tooth morphologies. Temporal and paleogeographic distributions of ‘haramiyidans’ indicate that they are a long-lasting and cosmopolitan group. |
